Remove DISALLOW_ macro from libcef_dll/ (see issue #3234)

Also perform related C++ cleanup:
- Use =default instead of {} for default implementations of
  constructors/destructors.
- Replace typedef with using.

libcef_dll/wrapper/cef_xml_object.cc

@@ -7,7 +7,6 @@
 #include <sstream>
 
 #include "include/base/cef_logging.h"
-#include "include/base/cef_macros.h"
 #include "include/cef_stream.h"
 
 namespace {
@@ -17,6 +16,9 @@ class CefXmlObjectLoader {
   explicit CefXmlObjectLoader(CefRefPtr<CefXmlObject> root_object)
       : root_object_(root_object) {}
 
+  CefXmlObjectLoader(const CefXmlObjectLoader&) = delete;
+  CefXmlObjectLoader& operator=(const CefXmlObjectLoader&) = delete;
+
   bool Load(CefRefPtr<CefStreamReader> stream,
             CefXmlReader::EncodingType encodingType,
             const CefString& URI) {
@@ -151,8 +153,6 @@ class CefXmlObjectLoader {
  private:
   CefString load_error_;
   CefRefPtr<CefXmlObject> root_object_;
-
-  DISALLOW_COPY_AND_ASSIGN(CefXmlObjectLoader);
 };
 
 }  // namespace